The present invention relates in general to active bolsters for occupant crash protection in automotive vehicles, and, more specifically, to an active bolster in a glove box door.
An active bolster is a vehicle occupant protection device with a gas-inflatable bladder to absorb impacts and reduce trauma to occupants during a crash. As opposed to deployable air bag cushions that emerge from behind various openings upon inflation, active bolsters use the interior trim surface itself to expand at the beginning of a crash event for absorbing the impact and dissipating energy through the action of an inflation gas. U.S. Pat. No. 8,205,909, issued Jun. 26, 2012, incorporated herein by reference, discloses an active knee bolster integrated into a glove box door that is light weight and visually attractive. U.S. Pat. No. 8,474,868, issued Jul. 2, 2013, also incorporated herein by reference, discloses a typical structure wherein an active bolster includes an outer wall or trim panel that faces a vehicle occupant attached to an inner wall or panel along a sealed periphery. One or both of the walls is deformable in order to provide an inflatable bladder. For example, the inner wall may have a pleated (i.e., accordion-like) region that straightens out during inflation. The walls are initially spaced apart by a small amount when in their pre-deployment, non-inflated condition. This allows ingress of the inflation gas in a manner that can achieve an even inflation across the panel.
The inner and outer walls of a typical active bolster are comprised of molded thermoplastics such as polyethylene, polyolefin, or PVC. They are typically injection molded but could also be blow molded. When formed separately, the walls must be hermetically joined around their periphery in order to form the inflatable bladder. The joint must be strong to resist separation as a result of the high pressures during inflation.
When incorporating an active bolster into the door for a glove box or other storage compartment, the inside back wall of the door is required to act as a reaction surface which must be relatively unmovable to that the inflating bladder and the front panel push outward, toward the vehicle occupant (instead of into the storage is compartment). The door typically spans the opening so that the edges of the door overlap with the instrument panel or compartment frame in order to stop the door movement at a closed position.
It is desirable to fabricate the back reaction wall from a moldable thermoplastic for low cost, low weight, and easy attachment to the bladder wall (e.g., by hot plate welding). One potential problem with such a reaction wall is that it may have sufficient flexibility to bend during deployment of the bolster. Particularly during the impact of a passenger against the front panel, the forces against the reaction wall may result in the submarining of the reaction wall through the door opening. The submarining can result in a partial loss of restraint force being applied toward the impacting body.